Acoustic air flow resistive article and method of making

ABSTRACT

An acoustic air flow resistive article and a method of making same. The acoustic air flow resistive article can include melt blown fibers having a fiber diameter of no greater than 10 μm and binder fibers dispersed amongst the melt blown fibers and at least partially melt-adhered to the melt blown fibers. The melt blown fibers can be formed of a resin having a first melting point, and the surface of the binder fibers can be at least partially formed of a resin having a second melting point that is less than the first melting point. The method can include mixing the melt blown fibers and the binder fibers to form a web, and pressing the web at a temperature that is less than the first melting point and greater than the second melting point.

FIELD

The present disclosure generally relates to an acoustic air flowresistive article, a production process thereof, and a sound-absorbingmember using the acoustic air flow resistive article.

BACKGROUND

Sound-proofing materials and sound-absorbing materials are used invarious settings to suppress noise. For example, dashboard insulatorsand floor insulators can be used as sound-absorbing and sound-proofingmaterials for automobile interiors to suppress engine room noise orsuppress noise entering from outside the vehicle. In some existingsystems, felt and other types of non-woven fabrics or moldable porousresins (e.g., composed of urethane foam) are used for thesesound-absorbing materials due to their low cost. In addition, in someexisting systems, required levels of sound-absorbing performance areobtained by increasing the thickness of these materials to enhance noiseabsorbing effects.

Patent Document 1 (Published Japanese Translation No. 2002-505209 of PCTInternational Publication No. WO 99/44817) describes a structure inwhich a second fiber layer composed of melt blown microfibers islaminated onto a first fiber layer composed of a non-woven fabric orplastic foam.

Patent Document 2 (Japanese Patent Application Laid-open No. 2003-49351)describes an automotive sound-absorbing material in which a melt blown,microfine fiber non-woven fabric is laminated onto one side of apolyester fiber non-woven fabric.

SUMMARY

A first aspect of the present disclosure provides an acoustic air flowresistive article. The acoustic air flow resistive article can includemelt blown fibers having a fiber diameter of no greater than 10 μm andbinder fibers dispersed amongst the melt blown fibers and at leastpartially melt-adhered to the melt blown fibers. The melt blown fiberscan be formed of a resin having a first melting point, and the surfaceof the binder fibers can be at least partially formed of a resin havinga second melting point that is less than the first melting point. Theacoustic air flow resistive article can include a solidity of at least10% and a weight per unit surface area that ranges from about 50 g/m² toabout 250 g/m².

A second aspect of the present disclosure provides a method of making anacoustic air flow resistive article. The method can include providingmelt blown fibers having a fiber diameter of no greater than 10 μm andproviding binder fibers. The melt blown fibers can be formed of a resinhaving a first melting point, and the surface of the binder fibers canbe at least partially formed of a resin having a second melting pointthat is less than the first melting point. The method can furtherinclude mixing the melt blown fibers and the binder fibers to form a webhaving a weight per unit surface area of about 50 g/m² to about 250g/m², and pressing the web at a temperature that is less than the firstmelting point and greater than the second melting point such that thesolidity of the web is at least about 10%.

A third aspect of the present disclosure provides a sound-absorbingmember. The sound-absorbing member can include a sound-absorbingmaterial having a surface adapted to face a sound source, and anacoustic air flow resistive article coupled to the surface of thesound-absorbing material.

Other features and aspects of the disclosure will become apparent byconsideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a sound-absorbing member accordingto one embodiment of the present disclosure, the sound-absorbing memberincluding an acoustic air flow resistive article and a sound-absorbingmaterial.

FIG. 2 is a cross-sectional view of a sound-absorbing member accordingto another embodiment of the present disclosure, the sound-absorbingmember including an acoustic air flow resistive article and an air layeras a sound-absorbing material.

FIG. 3 is an exploded view of a sound-absorbing member according toanother embodiment of the present disclosure, the sound-absorbing memberincluding an acoustic air flow resistive article and a spacer as asound-absorbing material.

FIG. 4 is a graph showing the sound-absorbing characteristics ofsound-absorbing members of examples and comparative examples of thepresent disclosure.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “supported,” and “coupled” and variations thereof are used broadlyand encompass both direct and indirect supports, and couplings. Further,the term “coupled” is not restricted to physical or mechanicalcouplings. It is to be understood that other embodiments may beutilized, and structural or logical changes may be made withoutdeparting from the scope of the present disclosure.

The present disclosure generally relates to an acoustic air flowresistive article having air flow resistance and can be capable ofimproving the acoustic properties of other sound-absorbing members bybeing coupled to (e.g., by laminating onto) the surface thereof; aproduction process thereof; and a sound-absorbing member comprising theacoustic air flow resistive article.

In some applications, such as in vehicles where shape and space arerestricted and the use of lightweight materials is required, it can bedifficult to obtain adequate noise suppression effects using felt andother conventional materials alone.

In sound-absorbing materials described in the aforementioned PatentDocuments 1 and 2, each of the laminates are composed only of melt blownfiber layers, and the materials have restorability even after beingpressed and adjusted for air flow rate due to the resiliency of thefiber layer. As a result, it is generally not easy to maintain the fiberlayer at a constant thickness. The inventors of the present disclosurehave discovered that this can make it difficult to control and maintainstable air flow characteristics, and that air flow resistance values canbe affected by factors such as fiber diameter, density of the fiberlayer, and/or thickness of the fiber layer.

Some embodiments of the present disclosure provide an acoustic air flowresistive article that is lightweight, thin and easily handled, and iscapable of stably adjusting air flow resistance of a sound-absorbingmaterial and improving the sound-absorbing performance thereof by beingcoupled to the surface of various sound-absorbing materials.

According to the acoustic air flow resistive article of a first aspectof the present disclosure, since solidity and weight per unit surfacearea are adjusted to predetermined values, a lightweight and thinarticle can be obtained that has high air flow resistance. In addition,since microfine melt blown fibers and binder fibers are included andpartially melt-adhered, the fiber structure can be fixed, making itpossible to provide stable air flow resistance characteristics whilefacilitating handling.

According to a manufacturing method of an acoustic air flow resistivearticle according to a second aspect of the present disclosure, bymixing microfine melt blown fibers having a fiber diameter of 10 μm orless with binder fibers followed by pressurizing at a temperature atwhich at least a portion of the binder fibers melt and controlling thethickness during pressurization, air flow resistance can be easilyadjusted, thereby providing the acoustic air flow resistive article of afirst aspect of the present disclosure. The thickness and fiberstructure of the pressed article can be fixed by the melted binderfibers to create an air flow resistive article having stable air flowresistance characteristics.

According to a sound-absorbing member according to a third aspect of thepresent disclosure, when the lightweight and thin acoustic air flowresistive article according to a first aspect of the present disclosureis coupled to a sound-absorbing material, high air flow resistancecharacteristics of the acoustic air flow resistive article can becontrolled, and can improve sound-absorbing characteristics withoutexcessively increasing weight or volume.

Acoustic Air Flow Resistive Article

The acoustic air flow resistive article of the present disclosure cangenerally be in the form of a web. In some embodiments, the acoustic airflow resistive article can be in the form of a film or a membrane.

The acoustic air flow resistive article of the present disclosure can becomprised of melt blown fibers and binder fibers. The binder fibers canbe dispersed among the melt blown fibers, and can be at least partiallymelt-adhered by the melt blown fibers to adjust the weight per unitsurface area and solidity of the acoustic air flow resistive article.

The term “binder fibers” generally refers to fibers of which at least aportion are melt-adhered to the melt blown fibers and are able todemonstrate the function of a binder.

In addition, the term “melt blown fibers” generally refers to a fibrousmaterial fabricated using a melt blowing method from a resin having amelting point greater than the melt-adhered portion of the binderfibers. Furthermore, this “melt blowing method” generally refers to amethod for processing fibers to have a narrow fiber diameter by meltinga resin material and spraying a high-temperature air flow onto a fibrousresin extruded from a nozzle.

The term “solidity” generally refers to a value determined by dividingthe bulk density of a web by the density of the material that composesthe web, and is expressed as a percentage. This solidity serves as anindicator of web filling, sealability, air flow and the like. Detailsregarding the measuring method thereof are described hereinafter.

The acoustic air flow resistive article can be used by coupling (e.g. bylaminating) directly or indirectly onto the surface of a sound-absorbingmaterial and the like, and can be a relatively thin web article thatimproves the sound-absorbing characteristics of the sound-absorbingmaterial by adjusting the air flow resistance thereof. Although theacoustic air flow resistive article can be used alone, thesound-absorbing effects can be improved by coupling the acoustic airflow resistive article to a sound-absorbing material, particularly, onthe side of the sound-absorbing material facing the sound source. As aresult, the air flow resistance of the sound-absorbing material can bemade to have a high air flow resistance substantially equal to that ofthe acoustic air flow resistive article. Namely, the air flow resistancevalue can be made to be constant regardless of the type ofsound-absorbing material with which it is combined.

In some embodiments, the acoustic air flow resistive article can becoupled directly or indirectly to a sound-absorbing layer. Thesound-absorbing layer can include, but is not limited to, one or more ofa felt layer, other nonwoven fabrics, an air layer, other suitablesound-absorbing materials, or combinations thereof.

The acoustic air flow resistive article and the sound-absorbing materialcan be coupled to a substrate, such as a vehicle body, to provide soundabsorption.

The following provides a more detailed explanation of embodiments of theacoustic air flow resistive article of the present disclosure.

In some embodiments of the present disclosure, the acoustic air flowresistive article has melt blown fibers having a fiber diameter of 10 μmor less, and binder fibers dispersed in the melt blown fibers and atleast partially melt-adhered to the melt blow fibers, wherein thesolidity of the article is at least 10% and the weight per unit surfacearea is about 50 g/m² to about 250 g/m².

In addition, in some embodiments, the air flow resistance (alsosometimes referred to herein as “air permeability”) of the acoustic airflow resistive article can be adjusted by adjusting the values forweight per unit surface area and solidity. In embodiments in which theweight per unit surface area is at least about 50 g/m² and the solidityis at least about 10%, an air flow resistance can be obtained that isgreater than that of felt and other conventional sound-absorbingmaterials. For example, in some embodiments, a value of at least about600 Pa*s/m can be obtained for air flow resistance.

Furthermore, in embodiments in which the weight per unit surface area isless than about 50 g/m², the acoustic air flow resistive article canbecome excessively thin, adequate strength may be unable to be obtained,and the density of the article can tend not to be uniform. As a result,in some embodiments, the weight per unit surface area is at least about50 g/m², which can facilitate ease of handling and can obtain uniformarticle density. In some embodiments, the weight per unit surface areais at least about 100 g/m², and in some embodiments, at least about 150g/m². In some embodiments, the weight per unit surface area is nogreater than about 250 g/m².

As mentioned above, in some embodiments, the air flow resistance isadjusted by adjusting the values of weight per unit surface area andsolidity. In general, the higher the solidity, the lower the void ratioin the acoustic air flow resistive article and the higher the air flowresistance that can be obtained. In some embodiments, solidity can beadjusted to at least about 15%, and in some embodiments, at least about18%. In addition, in embodiments in which solidity is constant, air flowresistance can be increased by increasing the weight per unit surfacearea. However, if the air flow resistance exceeds about 2500 Pa*s/m,sound reflection can occur in the acoustic air flow resistive article asa result of the occurrence of sound-proofing at high-frequency ranges,for example, at frequency ranges of at least about 3000 Hz, which canlead to a decrease in sound-absorbing characteristics. Thus, in the caseof making the weight per unit surface area about 250 g/m², for example,solidity can be 15% or less. On the other hand, in the case of makingthe weight per unit surface area 150 g/m² or less, for example, soliditycan be at least about 20%.

Furthermore, in some embodiments, air flow resistance is at least about600 Pa*s/m, in some embodiments, at least about 700 Pa*s/m, and in someembodiments, at least about 1000 Pa*s/m. In some embodiments, forexample to obtain satisfactory sound-absorbing characteristics even athigh-frequency ranges of at least about 3000 Hz as previously described,air flow resistance can be about 2500 Pa*s/m or less, and in someembodiments, about 2200 Pa*s/m or less.

Although solidity can be adjusted using various methods, it cantypically be adjusted by adjusting the thickness of the acoustic airflow resistive article, for example, by compressing the acoustic airflow resistive article at the time of production, as will besubsequently described. In some embodiments, the thickness of theacoustic air flow resistive article of the present disclosure can bemade to be no greater than about 3 mm, in some embodiments, no greaterabout 2 mm, and in some embodiments, no greater than about 1 mm.Furthermore, in some embodiments, the thickness of the acoustic air flowresistive article can be at least about 0.3 mm, and in some embodiments,at least about 0.5 mm in order to obtain adequate strength thereof.

Since the acoustic air flow resistive article of the present disclosurehas binder fibers dispersed in and melt-adhered to high melting pointmelt blown fibers, the structure of the melt blown fibers can be fixedresulting in the demonstration of stable air flow resistancecharacteristics.

In some embodiments, the content of the binder fibers per unit surfacearea of the acoustic air flow resistive article can be at least about 1g/m², and in some embodiments, can be at least about 5 g/m². If thecontent is less than 1 g/m², the amount of binder can be inadequate, andcan inhibit adequate melt-adhesion and stable fixation of the melt blownfiber structure, and can inhibit the maintenance of a constant air flowresistance due to recovery of the thickness of the article during use.On the other hand, if the amount of the binder is excessively high, theeffect of enhancing air flow resistance by the melt blown fibers can bediminished. As a result, in some embodiments, the content of the binderfibers is no greater than about 40 g/m², and in some embodiments, is nogreater than about 30 g/m².

The melt blown fibers are fibers that can be spun into microfine fibersby melt blowing, and there are no limitations thereon provided they havea higher melting point than a melting point of at least a portion of thesurface of the binder fibers. For example, the melt blown fibers can beselected from thermoplastic polymers such as polyethylene terephthalate(PET), polyethylene butylenes terephthalate (PBT),polyethylene-1,4-cyclohexane dimethanol (PCT), polylactic acid (PLA)and/or polypropylene (PP), polyacrylonitrile, polyacetate andpolyamide-based resins. Among these, PET and PP can be useful due totheir cost, processing ease, and the like. Moreover, PP can be usefulfrom the viewpoint of weight reduction due to its low specific gravity.

Furthermore, in the case of using a high-temperature step such as hotpressing as a method of, for example, laminating an acoustic air flowresistive article of the present disclosure onto a sound-absorbingmaterial in a subsequent step, it can be useful for the fibers of theacoustic air flow resistive article to have a comparatively high meltingpoint. In some embodiments, the melt blown fibers can have a meltingpoint of at least about 180° C. Examples of such fibers include, but arenot limited to, high ester-based fibers such as polyethylene butylphthalate (PBT) and amide-based fibers such as Nylon 6, Nylon 11 orNylon 66. Furthermore, the raw material of the melt blown fibers can beformed of a single material or a mixture of a plurality of resinmaterials.

In some embodiments, the diameter of the melt blown fibers is no greaterthan about 10 μm, in some embodiments, no greater than about 5 μm, andin some embodiments, no greater than about 3 μm. Such microfine fiberscan be fabricated by melt-blow spinning The use of microfine fibers cancreate a high air flow resistance at least partially because a morecomplex fiber structure having a finer pore diameter can be formed atthe same weight per unit surface area.

Furthermore, the term “fiber diameter” referred to herein generallyrefers to the average of the fiber diameter in a cross-sectionperpendicular to the long axis of the fibers. A geometric fiber diametercan be measured by direct observation using SEM photomicrographs or thelike. Also an effective fiber diameter can be theoretically determinedfrom the measured value obtained by measuring the pressure loss of theweb. A method of measuring the geometric fiber diameter is, for example,described in US Patent Application Publication No. 2004/00197155, thedisclosure of which is hereby incorporated by reference. The specificcalculation formula is described in greater detail in the Examplessection below. As used herein, the term “fiber diameter” refers to thegeometric fiber diameter.

At least a portion of the surface of the binder fibers has a lowermelting point than the melt blown fibers. For example, the melting pointof the low melting point portion of the binder fibers can be at leastabout 10° C., and in some embodiments at least about 20° C., lower thanthat of the melt blown fibers, and, for example, polyethyleneterephthalate (PET), polyethelene (PE) or polypropylene (PP) can beused. In the case of using, for example, polybutylene terephthalatehaving a melting point in the vicinity of 220° C. for the melt blownfibers, polyethylene terephthalate (PET) having a melting point in thevicinity of 100° C., and the like, can be used for at least a portion ofthe binder fibers.

Furthermore, in the case of using the acoustic air flow resistivearticle in a vehicle sound-absorbing construction, the melting point ofthe binder fibers can be about at least about 90° C., in someembodiments, at least about 100° C., and in some embodiments, at leastabout 120° C., to allow the fibers to withstand environmental tests.

The binder fibers may have a fibrous shape, and there are no particularlimitations on the cross-sectional diameter and length thereof. In someembodiments, short fibers can be used to enhance dispersibility. Forexample, staple fibers can be used that can be prepared by cutting spunfibers into lengths ranging from about 10 mm to about 100 mm.

Fibrous binder enables efficient melt adhesion with the melt blownfibers due at least in part to the high contact density therewith,thereby making it possible to suppress the required amount of lowmelting point binder.

The binder fibers are not required to be of a material having a uniformmelting point throughout, but rather can at least be provided with a lowmelting point layer on the surface thereof. For example, fibers having acore-sheath structure in which only the sheath portion has a low meltingpoint can be used. In some embodiments, during mixing with the meltblown fibers, only the low melting point binder of the sheath portionmelts, while the core portion remains in the form of fibers togetherwith the melt blown fibers. Thus, in some embodiments, the use of suchbinder fibers having a core-sheath structure can improve air flowresistance without disturbing the characteristic of the melt blownfibers.

In any case, the partially molten binder fibers can be melted andadhered to the melt blown fibers and can enhance air flow resistance ofhigh melting point melt blown fibers. In addition, stable air flowresistance characteristics can be provided as a result of being able tofix the melt blown fiber structure. In addition, increasing thestability of the air flow resistance characteristics can facilitatehandling of the acoustic air flow resistive article.

Sound-Absorbing Member

The acoustic air flow resistive articles of the present disclosure canbe used to form sound-absorbing members (e.g., laminated sound-absorbingmembers) by coupling the acoustic air flow resistive article to soundabsorbing materials.

FIG. 1 shows a sound-absorbing member 100 according to one embodiment ofthe present disclosure. The sound-absorbing member 100 comprises asound-absorbing material 120 and an air flow resistive article 110coupled onto a surface of the sound-absorbing material 120, for example,by laminating. The acoustic air flow resistive article 110 generallydoes not demonstrate much sound absorption alone. However, as shown inFIG. 1, by coupling the acoustic air flow resistive article 110 to thesurface of a sound-absorbing material 120, a sound-absorbing member 100can be formed, and the sound-absorbing characteristics of thesound-absorbing material 120 can be improved.

Here, “surface” refers to the side at which the sound to be absorbedenters, namely, the side facing the sound source. The air flowresistance of the entire sound-absorbing member can be determined bythat of the acoustic air flow resistive article, for example, inembodiments in which the acoustic air flow resistive article having ahigh air flow resistance is provided on the surface of thesound-absorbing member.

Furthermore, there are no limitations on the type of sound-absorbingmaterial 120 to which the acoustic air flow resistive article 110 iscoupled, and various sound-absorbing materials can be used. For example,not only conventional sound-absorbing materials such as felt or urethanefoam, but also various other sound-absorbing materials can be used.Further, combined or complex plural materials including anothermelt-blown fiber layer can be used. When sound-absorbing materialshaving lower air flow resistance than the acoustic air flow resistivearticle are used, the effect of coupling the acoustic air flow resistivearticle can be particularly obtained. There is no limitation of thethickness of the sound-absorbing materials. For example, the thicknesscan vary from several millimeters to several tens of millimeters, andthe thickness can be changed depending on the application.

FIG. 2 shows a sound-absorbing member 200 according to anotherembodiment of the present disclosure. The sound-absorbing member 200comprises an acoustic air flow resistive article 210 and an air layer220. The air layer 220 serves as the sound-absorbing material, and thesound-absorbing member 200 can further include or be coupled to aportion of a substrate member 230 (e.g., a vehicle body). Thesound-absorbing member 200 can also further include or be coupled tosupporting materials 240, which are provided between the acoustic airflow resistive article 210 and the substrate member 230. Various spacerssuch as mesh materials or honeycombs having a high degree of airpermeability can be used as the supporting materials 240, as will bedescribed with respect to the embodiment in FIG. 3.

FIG. 3 shows an exploded view of a sound-absorbing member 300 accordingto another embodiment of the present disclosure. The sound-absorbingmember 300 comprises an acoustic air flow resistive article 310 coupledto a substrate member 330 using a supporting material 340. Each of thesubstrate member 330 and the supporting material 340 can form a portionof or be coupled to the sound-absorbing member 300. In the embodimentillustrated in FIG. 3, the supporting material 340 is in the form of aspacer. By way of example only, in the embodiment illustrated in FIG. 3,the spacer 340 can include a honeycomb made of metal films, paper, resinfilm, or the like, and having a layer thickness of 2 mm to 20 mm,partition wall having thickness of 0.5 mm to 1 mm and a cell pitch of 5mm to 20 mm. In this case, an extremely lightweight sound-absorbingmember 300 can be obtained.

A sound-absorbing member obtained in this manner is able to demonstratehigh sound-absorbing characteristics over a wide range of wavelengths,for example, from about 100 Hz to about 3000 Hz.

Manufacturing Process of Acoustic Air Flow Resistive Article

The production process of the acoustic air flow resistive article of thepresent disclosure consists of first mixing melt blown fibers having aparticle diameter of no greater than 10 μm with binder fibers, andforming a web having a weight per unit surface area of 50 to 250 g/m².In this step, an ordinary melt blowing process can be used to blow thebinder fibers so as to directly converge with an air flow containingblown melt blown fibers, and form a web in which the binder fibers aresubstantially uniformly dispersed among the melt blown fibers. Thebinder fibers can be blown together by highly pressurized air flow aftersleaving fibers with a rotating body such as a Rikken roll.Comparatively short fibers can be used to improve dispersibility of thebinder fibers. In addition, the weight per unit surface area can beadjusted with the amount of each fiber blown into the compressed gasflow.

The process of mixing melt blown fibers with binder fibers is notlimited by the above-mentioned process. For example, the followingprocess can be used, which is described in U.S. Pat. No. 4,813,948, thedisclosure of which is hereby incorporated by reference. First, a meltblown fiber web can be prepared by using a conventional melt blownprocess. Then, a combined web can be formed by introducing the meltblown fiber web in an air-laying apparatus at a feed roll to a lickerinwith binder fibers. The lickerin can divellicate the melt blown fiberweb. In some embodiments, the melt blown fiber web can be coated with asurfactant at least partially before introducing the melt blown fibersto the air-laying apparatus.

Next, the resulting combined web can be compressed by pressing fromabove and below in the direction of the thickness thereof at atemperature at which at least the surfaces of the binder fibers melt toform a combined web having a solidity of at least about 10%. There areno limitations on the heating method, and various methods, such as theuse of a lamp or the use of a heater can be used. In addition, anymethod can be used for pressing, such as the use of a pressing machineor pressing rollers. In some embodiments, the combined web can be heatedfirst and then pressed. In some embodiments, heating and pressurizationcan be carried out simultaneously, for example, using an ordinarycalendering step. The heating conditions can be such that the heatingtemperature is a temperature at which at least a portion of the binderfibers melt but the melt blown fibers do not. Furthermore, it is notnecessary for the entirety of the binder fibers to melt, but rather onlythe portion capable of adhering and fixing the fiber structure isrequired to be melted. In the case of using binder fibers having acore-sheath structure, conditions may be used under which only thesheath portion melts.

Furthermore, adjustment of solidity and air flow resistance in themethod described above can be adjusted primarily with the thickness ofthe web during pressurization. For example, air flow resistance can beadjusted by adjusting the gap between pressing rollers. As a result, thethickness of the acoustic air flow resistive article of the presentdisclosure can be processed to be extremely thin, for example, in someembodiments, no greater than about 3 mm, in some embodiments, no greaterthan about 1 mm, and in some embodiments, no greater than about 0.5 mm.

In addition, the molten binder fibers can stably maintain air flowresistance characteristics of the acoustic air flow resistive article,even if subjected to various deformations and processing, because thebinder fibers can firmly fix the fiber structure of the acoustic airflow resistive article.

As mentioned above, the acoustic air flow resistive article can becoupled (e.g., by laminating) to a sound-absorbing material to form asound-absorbing member. One exemplary method for coupling the acousticair flow resistive article to a surface of a sound-absorbing material(e.g., felt or urethane foam) includes integrating the ends of theacoustic air flow resistive article and the sound-absorbing materialinto a single unit. For example, the ends can be integrated by hotpressing the sound-absorbing member either before, during, or aftercutting the sound-absorbing member to a predetermined pattern.Alternatively, each layer of the sound-absorbing member can be coupledtogether by other means (e.g., via adhesive materials).

Application of Acoustic Air Flow Resistive Article

A sound-absorbing member (e.g., a laminated sound-absorbing member)using the acoustic air flow resistive article of the present disclosurecan be used in a wide range of applications including, but not limitedto, automobile dashboard insulators, flow insulators, automobile roofingconstructions, automobile door constructions, the walls and floors ofresidences, and various other applications requiring sound insulation.In particular, since the acoustic air flow resistive article of thepresent disclosure is generally thin and lightweight, it can be used incombination with various sound-absorbing materials. In addition, asound-absorbing member using an air layer for the sound-absorbingmaterial can be obtained, for example, by providing a gap (e.g., a fixedgap) between the acoustic air flow resistive article and a substrate(e.g., a vehicle body, automobile interior, etc.) to which the articleis coupled.

EXAMPLES

The following working examples are intended to be illustrative and notlimiting, and the present invention is not limited to the descriptionsof these examples. First, an explanation is provided of the methods usedto measure various values used to evaluate the following examples andcomparative examples.

Weight Per Unit Surface Area: Units (g/m²)

The weight per unit surface area of an acoustic air flow resistivearticle is measured in the following manner. Five acoustic air flowresistive articles cut to a size of 10 cm×10 cm were prepared, eachsample was weighed, and the weight per unit surface area was determinedfrom the average thereof.

Solidity: Units (%)

As indicated by the following equation, solidity is the value determinedby dividing the bulk density of the acoustic air flow resistive articleρ(web) by the density of the material that composes the acoustic airflow resistive article ρ(material), and is expressed as a percentage.The bulk density of the acoustic air flow resistive article ρ(web) isdetermined by dividing the weight per unit surface area of the acousticair flow resistive article as determined using the method describedabove by the thickness. Furthermore, although the thickness of theacoustic air flow resistive article was measured in compliance with ASTMF778-88, the method for measuring the thickness is describedhereinafter. In addition, material density ρ(material) was determinedfrom the raw material densities of the melt blown fibers and binderfibers provided by the manufacturers supplying the raw materials.

Solidity(S)=[ρ(web)/ρ(material)]×100(%)  Equation 1

-   -   ρ(web): Bulk density of acoustic air flow resistive article    -   ρ(material): Density of material composing acoustic air flow        resistive article        where,

ρ(material)=(ρ(h)·X1/100)+(ρ(1)·X2/100)

-   -   ρ(h): Density of melt blown fibers    -   ρ(1): Density of binder fibers    -   X1: Weight ratio of melt blown fibers (%)    -   X2: Weight ratio of binder fibers (%)

Air Flow Resistance (Pa*s/m)

Air flow resistance was measured based on the method described in ASTM C522. Samples of the examples and comparative examples were cut intocircles measuring 5.25 inches (13.33 mm) in diameter and fixed to asample stand. Compressed air was supplied in the direction perpendicularto 100 cm² of the sheet surface followed by measurement of the resultingpressure difference in the direction perpendicular to the surface of theacoustic air flow resistive article.

Measurement of Sound Absorption

Sound-absorbing characteristics were measured using the two microphonemethod based on ASTM E 1050-98 (“Impedance and Absorption Using a Tube,Two Microphones and a Digital Frequency Analysis System”). The measuringrange was 500 to 4000 Hz. The two microphone method measures theincident and reflected components of sound pressure within a tube withtwo microphones to determine the sound absorption coefficient.

In addition, the speech interference level (SIL) was determined usingthe resulting sound absorption coefficient data. Speech interferencelevel (SIL) is an indicator used to evaluate noise environments as tothe degree to which speech can be succinctly comprehended in thepresence of peripheral noise in the case of persons with normal hearinglevels speaking directly in an unaided voice without using earphones ormegaphone or the like. The SIL is defined as the arithmetic average ofthe noise sound pressure levels (A characteristics) of four bands havingcentral frequencies of 500, 1000, 2000 and 4000 Hz.

Fiber Diameter

1. Geometric Fiber Diameter

The geometric fiber diameter for each web sample of each example orcomparative example were determined by image analysis of SEMphotomicrographs of a web specimen (“geometric diameter” herein means ameasurement obtained by direct observation of the physical dimension ofa fiber, as opposed, for example, to indirect measurements such as thosethat give an “effective fiber diameter”).

Small web samples having a size of 1 cm×1 cm were cut from web samples.Each small web sample was then inserted into a scanning electronmicroscope S-3500N (Hitachi High Technology Inc., Japan) and was imagedusing a beam energy of 20 keV, a working distance of approximately 15mm, and a 0 degree sample tilt. Note that in the SEM analysis, metalcoating of the sample was unnecessary. Electronic images taken at 500and 1000 times magnification were used to measure fiber diameters. Toperform the image analysis for each small web sample, five to ten fiberswhich appeared to be subject fibers were selected and the diameter ofthe subject fibers were measured by using the scale bar on the image. Anaverage of the diameters was calculated.

2. Effective Fiber Diameter

The effective fiber diameter (EFD), determined according to the equationshown below was used for the fiber diameter of the melt blown fibers.

EFD=27.68×{[(A ^(1.5)+1254.37×A ^(4.5))×L]/ΔP/9.8}^(0.5)  Equation 2

where,

-   -   ΔP is the pressure loss (Pa), and    -   “A” is represented by the equation below:

A=BW/(R×L)

-   -   BW: Sample weight (g)    -   R: Sample density (g/cm³)    -   L: Sample thickness (mm)

Article Thickness: (mm)

The thickness of the acoustic air flow resistive article was measuredusing a measurement apparatus having two plates movable in a verticaldirection (i.e., up-and-down) and a micrometer measuring the distancebetween the two plates according to ASTM F778-88. During measurement,five acoustic air flow resistive articles cut to a size of 10 cm×10 cmwere prepared. A weight of 16 g was placed on the top plate of themeasurement apparatus, and the top plate was then raised. An acousticair flow resistive article sample was positioned at the center of thebottom plate of the measurement apparatus, and then the top plate wasreleased from a height of 1.0 cm+/−0.2 cm. After waiting at least 3seconds, the distance between the two plates was measured, namely, thethickness of the acoustic air flow resistive article was measured. Thethickness of each sample was measured and an average for each articlewas obtained.

Example 1

Melt blown fibers having a fiber diameter of 5 μm were spun to a weightper unit surface area of 120 g/m² from PBT resin (DURANEX® PBT 2002 meltblown fibers, available from Win Tech Polymer ltd., Tokyo, Japan) in amelt blowing process. Binder fibers having a core-sheath structurehaving a fiber diameter of 2.2 denier and average fiber length of 38 mm,in which the core was made of PET having high temperature melting pointof 260° C. and sheath was made of PET having low temperature meltingpoint of 100° C. (TEIJIN-TETRON® TJO4C2 binder fibers, available fromTeijin Fiber Ltd., Osaka, Japan), were used. The binder fibers wereblown to 5 g/m² using binder fibers so as to merge with the fiber flowimmediately after the above melt blown fibers were blown to produce acombined web having a total weight per unit surface area of 125 g/m².Namely, 4.0 wt % of the binder fibers were added to the total combinedweb. This combined web was crushed using a roller heated to 110° C. toobtain an acoustic air flow resistive article having a thickness of 0.5mm. The solidity of this acoustic air flow resistive article was 18%.

This acoustic air flow resistive article was laminated onto PET felthaving a weight per unit surface area of 325 g/m² and thickness of 7 mmto produce a laminated sound-absorbing member.

Example 2

A combined web having a weight per unit surface area of 130 g/m² andthickness of 0.9 mm was produced by mixing binder fibers at 10 g/m² intomelt blown fibers. Namely, 7.7 wt % of the binder fibers were added tothe total combined web. The solidity of this acoustic air flow resistivearticle was 11.0%. Other conditions were the same as those used inExample 1.

Example 3

A combined web having a weight per unit surface area of 127 g/m² andthickness of 0.5 mm was produced by mixing binder fibers at 10 g/m² intomelt blown fibers. Namely, 7.9 wt % of the binder fibers were added tothe total combined web. The solidity of this acoustic air flow resistivearticle was 20.8%. Other conditions were the same as those used inExample 1.

Example 4

A combined web having a weight per unit surface area of 142 g/m² andthickness of 1.0 mm was produced by mixing binder fibers at 30 g/m² intomelt blown fibers. Namely, 21 wt % of the binder fibers were added tothe total combined web. The solidity of this acoustic air flow resistivearticle was 11.2%. Other conditions were the same as those used inExample 1.

Example 5

A combined web having a weight per unit surface area of 250 g/m² andthickness of 1.7 mm was produced by mixing binder fibers at 5 g/m² intohigh melting point melt blown fibers. Namely, 2.0 wt % of the binderfibers were added to the total combined web.

The solidity of this acoustic air flow resistive article was 11.2%.Other conditions were the same as those used in Example 1.

COMPARATIVE EXAMPLE 1

A sound-absorbing member composed of PET felt having a weight per unitsurface area of 325 g/m² and thickness of 7 mm was used without using anacoustic air flow resistive article.

COMPARATIVE EXAMPLE 2

A web having a weight per unit surface area of 118 g/m² and thickness of1.8 mm composed only of melt blown fibers was produced without mixingwith binder fibers. The solidity of the web was 4.9%. Other conditionswere the same as those used in Example 1.

COMPARATIVE EXAMPLE 3

A combined web having a weight per unit surface area of 138 g/m² andthickness of 2.9 mm was produced by mixing binder fibers at 30 g/m² intomelt blown fibers. Namely, 22 wt % of the binder fibers were added tothe total combined web. The solidity of the combined web was 3.7%. Otherconditions were the same as those used in Example 1.

COMPARATIVE EXAMPLE 4

A combined web having a weight per unit surface area of 375 g/m² andthickness of 2 nun was produced by mixing binder fibers at 15 g/m² intomelt blown fibers. Namely, 4.0 wt % of the binder fibers were added tothe total combined web. The solidity of the combined web was 3.7%. Otherconditions were the same as those used in Example 1.

COMPARATIVE EXAMPLE 5

A PET non-woven fabric having a fiber diameter of 44 μm, weight per unitsurface area of 100 g/m² and thickness of 0.6 mm was produced using theSpanbond method instead of using melt blown fibers. Felt having athickness of 7 mm was laminated onto this PET non-woven fabric.

COMPARATIVE EXAMPLE 6

A PET non-woven fabric having a fiber diameter of 23 μm, weight per unitsurface area of 90 g/m² and thickness of 0.6 mm was produced using theneedle punch method instead of using melt blown fibers. Felt having athickness of 7 mm was laminated onto this PET non-woven fabric.

Evaluation

The conditions of each of the examples and comparative examples alongwith the sound-absorbing characteristics thereof are shown in Table 1and FIG. 4.

The embodiments described above and illustrated in the figures arepresented by way of example only and are not intended as a limitationupon the concepts and principles of the present disclosure. As such, itwill be appreciated by one having ordinary skill in the art that variouschanges in the elements and their configuration and arrangement arepossible without departing from the spirit and scope of the presentdisclosure. Various features and aspects of the present disclosure areset forth in the following claims.

TABLE 1 High melting Weight per Air point melt unit surface Thicknesspermeability Solidity blown fiber Sound absorption coefficient (—) area(g/m²) (mm) (Pa * s/m) (%) diameter (μm)* 500 Hz 1000 Hz 2000 Hz 4000 HzSIL Ex. 1 125 0.5 1267 18 G: 4 0.139 0.417 0.875 0.962 0.599 EED: 5 Ex.2 130 0.9 754 11.0 G: 4 0.158 0.377 0.837 0.947 0.580 EFD: 5 Ex. 3 1270.5 1343 20.8 G: 4 0.118 0.387 0.815 0.949 0.567 EFD: 5 Ex. 4 142 1.0979 11.2 G: 5 0.185 0.416 0.821 0.950 0.593 EFD: 5 Ex. 5 250 1.7 219311.2 G: 4 0.184 0.450 0.885 0.951 0.617 EFD: 5 Comp. — — — — — 0.07450.182 0.416 0.774 0.362 Ex. 1 Comp. 118 1.8 184 4.9 G: 4 0.149 0.2920.644 0.951 0.509 Ex. 2 EFD: 5 Comp. 138 2.9 184 3.7 G: 4 0.142 0.2990.638 0.966 0.511 Ex. 3 EFD: 5 Comp. 375 2 4428 14.9 G: 4 0.186 0.6570.758 0.681 0.571 Ex. 4 EFD: 5 Comp. 100 0.6 18.4 12.7 G: 42 0.09410.189 0.443 0.812 0.385 Ex. 5 EFD: 44 Comp. 90 0.6 55.2 11.5 G: 18 0.1090.217 0.496 0.855 0.419 Ex. 6 EFD: 23 *“G” refers to geometric fiberdiameter and “EFD” refers to effective fiber diameter.

1. An acoustic air flow resistive article comprising: melt blown fibershaving a fiber diameter of no greater than 10 μm, the melt blown fibersbeing formed of a resin having a first melting point; and binder fibersdispersed amongst the melt blown fibers and at least partiallymelt-adhered to the melt blown fibers, the surface of the binder fibersbeing at least partially formed of a resin having a second melting pointthat is less than the first melting point, wherein the solidity is atleast 10% and the weight per unit surface area ranges from about 50 g/m²to about 250 g/m².
 2. The acoustic air flow resistive article accordingto claim 1, wherein the thickness of the acoustic air flow resistivearticle is no greater than 2 mm.
 3. The acoustic air flow resistivearticle according to claim 1, wherein the air flow resistance of theacoustic air flow resistive article ranges from about 600 Pa*s/m toabout 2500 Pa*s/m.
 4. The acoustic air flow resistive article accordingto claim 1, wherein the melt blown fibers comprise one or a plurality offibers selected from polyester or amide fibers having a melting point ofat least 180° C., and wherein the binder fibers comprise staple fibersin which at least a portion of the surface of the staple fibers has amelting point of at least 90° C. and less than 180° C.
 5. The acousticair flow resistive article according to claim 1, wherein the binderfibers are included at a weight per unit surface area of about 1 g/m² toabout 40 g/m².
 6. The acoustic air flow resistive article according toclaim 1, wherein the binder fibers have a core-sheath structure and onlythe sheath portion of the binder fibers is melt-adhered to the meltblown fibers.
 7. A sound-absorbing member comprising: a sound-absorbingmaterial having a surface adapted to face a sound source; and theacoustic air flow resistive article according to claim 1 coupled to thesurface of the sound-absorbing material.
 8. The sound-absorbing memberaccording to claim 7, wherein the sound-absorbing material comprises anair layer.
 9. A method of making an acoustic air flow resistive articlecomprising: providing melt blown fibers having a fiber diameter of nogreater than 10 μm, the melt blown fibers being formed of a resin havinga first melting point; providing binder fibers, the surface of thebinder fibers being at least partially formed of a resin having a secondmelting point that is less than the first melting point; mixing the meltblown fibers and the binder fibers to form a web having a weight perunit surface area of about 50 g/m² to about 250 g/m²; and pressing theweb at a temperature that is less than the first melting point andgreater than the second melting point such that the solidity of the webis at least about 10%.
 10. The method according to claim 9, whereinpressing the web includes pressing the web to a thickness of no greaterthan 2 mm.